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  Direct current motorUSPTO Application #: 20080093947Title: Direct current motor Abstract: A stator has four or more magnetic poles. A commutator has a plurality of segments arranged in the circumferential direction and a short-circuit conductor for short-circuiting predetermined segments from among these segments. Each segment has an angular width WS, and there is a gap of an angular width WU between the segments. A substantial angular width WB of each of an anode brush and a cathode brush satisfies (n−1)(WS+WU)+WU<WB<n(WS+WU)+WU, where n is an integer no less than two. A plurality of coils are each connected to the corresponding one of the segments in order to form n closed loops. The closed loops each pass through the corresponding segments and are electrically independent of each other. (end of abstract) Agent: Marsh, Fischmann & Breyfogle LLP - Aurora, CO, US Inventors: Tomohiro Aoyama, Yasuhide Ito, Toshio Yamamoto USPTO Applicaton #: 20080093947 - Class: 310197 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080093947. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]The present invention relates to a direct current motor provided with a stator having four or more magnetic poles. [0002]The direct current motor disclosed in Japanese Laid-Open Patent Publication 2004-88915 has a stator where magnets are placed to form four or more magnetic poles. The rotary shaft rotates integrally with an armature core and a commutator core, and the armature core has a plurality of coils. The commutator has a plurality of segments arranged in the circumferential direction, and a short-circuit conductor for short-circuiting predetermined segments to each other. The coils are each connected to corresponding segments such that one closed circuit (closed loop) including the short-circuit conductor and all of the coils is formed between an anode brush and a cathode brush which contact and slide against the segments. [0003]In the direct current motor in the above described publication, however, the number of closed loops including the short-circuit conductor and all of the coils is one. Therefore, it is necessary for the cross-sectional area of the short-circuit conductor to be large, in order to prevent the density of the main current flowing through the short-circuit conductor from becoming too high. As a result, the space in which the short-circuit conductor is placed becomes large, making the commutator and the direct current motor large. In the case where the short-circuit conductor is short-circuit wires made of conducting wire, for example, it is necessary for the space between the commutator where short-circuit wires are placed and the armature core in the axial direction to be set large. In addition, in the case where the short-circuit conductor is a great number of short-circuit pieces formed through punching out a conductor plate, the commutator having these short-circuit pieces becomes large. SUMMARY OF THE INVENTION [0004]An objective of the present invention is to provide a direct current motor that reduces the size of the short-circuit conductor (reduction in the size of a space for accommodating the short-circuit conductor). [0005]According to one aspect of the present invention, a direct current motor provided with a stator having four or more magnetic poles is provided. An armature is rotatable relative to the stator. The armature is provided with an armature core and a commutator which rotate integrally. The armature core has a plurality of teeth and a plurality of coils which are respectively wound around these teeth. The commutator has a plurality of segments arranged in a circumferential direction, and a short-circuit conductor for short-circuiting predetermined segments from among these segments. Each segment has an angular width WS, and there is a space of an angular width WU between each adjacent pair of the segments. An anode brush and a cathode brush contact and slide against the respective segments when the commutator rotates. The respective practical angular widths WB of the anode brush and the cathode brush satisfy (n-1)(WS+WU)+WU<WB<n(WS+WU)+WU, where n is set to be an integer no less than two. The coils are respectively connected to the corresponding segments, in order to form n closed loops which pass through the respective corresponding segments, and are electrically independent of each other. [0006]Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0007]The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: [0008]FIG. 1 is a plan view showing a direct current motor according to a first embodiment of the present invention; [0009]FIG. 2 is a longitudinal cross-sectional view showing the motor of FIG. 1; [0010]FIG. 3 is a plan view showing the short-circuit members shown in FIG. 2; [0011]FIG. 4 is a plan view showing only the short-circuit pieces shown in FIG. 3; [0012]FIG. 5 is a developed view showing the motor of FIG. 1; [0013]FIG. 6 is a developed view showing the state after the commutator has rotated from the state in FIG. 5; [0014]FIG. 7 is a view showing a circuit formed of a plurality of coils shown in FIG. 5; [0015]FIGS. 8A and 8B are front views showing the anode brush and three segments shown in FIG. 2; [0016]FIG. 9A is a graph showing the time-resistance plot between a coil M1 and the anode brush in FIG. 8A; [0017]FIG. 9B is a graph showing the time-current plot of the coil M1 in FIG. 8A; [0018]FIG. 10 is a developed view showing a direct current motor according to a second embodiment of the present invention; [0019]FIG. 11 is a view showing operation of the direct current motor of FIG. 10; [0020]FIG. 12 is a developed view showing a direct current motor according to a third embodiment of the present invention; [0021]FIG. 13 is a developed view showing a direct current motor according to a fourth embodiment of the present invention; Continue reading... Full patent description for Direct current motor Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Direct current motor patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Direct current motor or other areas of interest. ### Previous Patent Application: Electric generator Next Patent Application: Rotary electric machine, crank-shaped continuously winding coil, distribution winding stator and forming method thereof Industry Class: Electrical generator or motor structure ### FreshPatents.com Support Thank you for viewing the Direct current motor patent info. 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